Height HETP

The A term represents the contribution from eddy diffusion, the B term the contribution from longitudinal diffusion, and the C terms the contributions from mass transfer in the mobile and stationary phases to the total column plate height. By differentiating equation (1.31) with respect to the mobile phase velocity and setting the result equal to zero, the optimum values of mobile phase velocity (u ) and plate height (HETP ) can be obtained. [Pg.15]

In order to evaluate the efficacy of the expanded bed technique the plate height (HETP), plate number (N), resolution (Rs), Bodenstein number (Bo), particle Peclet number (Pep) and axial dispersion coefficient (DJ have been calculated and compared with the corresponding values of a traditional HPLC column. N can be expressed by... [Pg.21]

I. Height Equivalent of a Theoretical Plate or Plate Height (HETP or H)... [Pg.27]

Another example is the confusion between the terms efficiency, efficacy, and selectivity of a separation. It is not always mentioned how these responses are obtained. Usually, the efficiency is either expressed as the number of theoretical plates or plate number, N, or as the height equivalent to a theoretical plate or plate height, HETP or With efficacy, usually efficiency, thus plate count, is meant, although it is not always clearly specified. The selectivity, in general, is found by calculating the selectivity or separation factor, a, which is a measure for the... [Pg.210]

TABLE 3.10 Packing Height HETP, ft, Required Related to Tray Efficiency... [Pg.114]

In chromatography, the van Deemter equation relates the theoretical column-plate height (HETP) to which of the following ... [Pg.27]

The first notable point Is that the minimum plate heights are the same. This Is reasonable and predictable since the minimum plate height (HETP j n) In a van Deempter curve for a packed column Is a function of the packing particle diameter (dp) and the analyte capacity factor (k ) ... [Pg.137]

Every stage requires a certain column height HETP (height equivalent to a theoretical plate) however, dealing with the design of an industrial chromatography column it is necessary to take into account that... [Pg.543]

In this section it has been shown that the integration of the general equation (9.8-27) leads to concentration profiles in adsorbent packings. In Chaps. 5 and 6, the concept of the number N of stages and the height HETP (height equivalent to a theoretical plate) was introduced. The application of this model leads to the general equation... [Pg.547]

The efficiency of chromatographic separations can be determined by calculating the plate heights. For the SDC system, the theoretical plate height (HETP) can be calculated using Eq. 3 ... [Pg.2980]

Higher diffusion coefficients translate directly to higher speed chromatography as indicated in the van Deemter equation. Figure 2 is a van Deemter plot of plate height (HETP) versus linear velocity for both... [Pg.4569]

Figure 2 A van Deemter plot of plate height (plate height = HETP = height equivalent of a theoretical plate) vs. linear velocity showing that SFC exhibits similar, low (good) plate heights but at much higher velocities (and flow rates) compared to HPLC. Lines A, B, and C represent efficiency vs. flow on 10, 5, and 3 pm particles, respectively. Lines D and E represent HPLC on 10 and 3 pm particles, respectively.

H Plate height HETP Height equivalent to one theoretical plate... [Pg.114]

The UPLC is based on the same principle as HPLC, namely adsorption chromatography using an adsorbent of very fine size, to increase the surface area and thus adsorption. The stationary phase in UPLC consists of particles less than 2.0 pm, while HPLC columns are typically filled with particles of 3-5 pm. The underlying principles of this evolution are also governed by the van Deemter equation, which is an empirical formula that describes the relationship between linear velocity (flow rate) and plate height (HETP or column efficiency). Naturally, the column length has to be less and much higher pressure is needed to maintain percolation... [Pg.10]

PLATE HEIGHT (HETP or H). Indicates the diffusion or broadening of the zones during migration. The length of the layer divided by the number of plates (N). A small plate height results in better resolution. [Pg.481]

Thus, a minimum of more than 400 theoretical plates is required to achieve the desired separation this is an enormous number. Fortunately, high-efficiency packings are now available with equivalent heights HETP of the order of 1 cm. This limits the size of the column to heights that are not excessive and can be implemented in practice. [Pg.290]

Retention time and peak standard deviation are also used in the characterization of the column efficiency, i.e., in the calculation of the plate number N (Eq. 4) and the plate height //(HETP = height equivalent to a theoretical plate) (Eq. 5). By combining these equations, the resolution can be written as... [Pg.8]

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